1. Field of the Invention
This invention relates to microfilm projectors and, in particular, those projectors adapted for use with microfilm wound on a reel.
2. Description of the Prior Art
Microfiche readers and reader/printers (hereinafter referred to only as readers) have been known and used in the microfilm arts for years. The material projected was always an image from a frame on the microfiche representing one document. Conventional microfiche readers are disclosed in such patents as U.S. Pat. No. 3,616,737 and U.S. Pat. No. 4,025,177.
A subspecies of microfiche readers includes an adapter to accommodate microfilm in reel form and transport the film to a viewing area which includes a glass plate located at the focal plane of the optics of the microfilm reader.
The purpose of the present invention is to allow the user of such a microfilm reader to mask unwanted information from a document by placing a mask in the area of the microfilm to permit selective projection and display or printing of only a portion of the information found on the frame of microfilm.
The present invention allows the user to select information to be viewed or printed and to obscure irrelevant or confidential information from a document. As an example, a credit record from client A may be read and/or printed while credit records of client B on the same frame of microfilm may be omitted.
Related to microfilm projectors are overhead projectors which project images from a transparency containing information in a non-reduced form. Overhead projectors such as those shown in U.S. Pat Nos. 3,269,261; 3,531,193 and 3,661,449 describe plates which are slideable with respect to a transparency to prevent readers from reading ahead of the material presently being discussed. U.S. Pat. No. 3,342,101 describes an overhead projector which includes a movable ruler which may be positioned to obscure a portion of a transparency. Although all of these devices associated with overhead projectors may be considered to be information masks, their teachings are not directly transferable to the microfilm arts wherein the information contained on the transparent film is greatly reduced in size.